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Site Conceptual Models

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Presentation on theme: "Site Conceptual Models"— Presentation transcript:

1 Site Conceptual Models
Keith Kezer SAM Project Manager General introduction of myself. Laidlaw Environmental – Field Chemist 1. Package and transport hazardous materials 2. Remedial activities including excavation TRC – Staff level to Senior Management Level 1. Started as entry level field grunt (field work, research, report preparation) 2. Managed intricate programs for a couple major oil companies County of San Diego – Project Manager 1. Previous experience as a consultant helped enormously

2 Why a discussion on SCMs?
Confusion on exactly what a SCM is Clarify the goals of a SCM Provide guidance on when a SCM is necessary Have consistency on the contents of SCMs Provide opportunity to address consultant questions and provide clarifications. The confusion about SCMs is evident in discussions with multiple consultants and review of reports.

3 How many think this a SCM?
There are some good ideas in this figure related to exposure concerns but we’ll have to see in terms of a site conceptual model

4 SCM questions received by DEH
Why do we need to submit boring logs and cross sections? Why do we need to re-submit information that was already submitted to DEH? Why must a receptor pathway evaluation be included in a site assessment report? For those of you who question the necessity of a SCM discussion I have a couple of questions we have received repeatedly at the DEH. I’d like to take just a minute or two to briefly discuss their importance. Boring logs and Cross Sections a. To better understand the relationship of underground structures (utilities, water ways) and geology to contaminant locations and how and why contaminants are migrating (i.e. through sand layers, on clay layers etc.) 2. Information Re-submittal a. The typical DEH project manager has approximately 100 cases that they manage. If the information is not provided with each report DEH staff would have to memorize it or spend countless hours reviewing files. b. The typical case has 5 to 15 folders of information, many of them 20 to 30 folders which is lot of information to sort through to find a simple fact like whether or not a site passed a benzene vapor risk assessment. c. A site conceptual model is comprehensive in nature. 3. A receptor pathway evaluation a. DEH uses a risk based cleanup approach, risk is defined as receptors and the potential for them to be impacted. b. Conditions may change even if assessment activities are complete (i.e. groundwater elevation increases) c. A receptor pathway evaluation must be updated as assessment continues at the site.

5 SCM Definition Keith Kezer Definition:
A comprehensive compilation of data, interpretations, and site specific circumstances which describe and explain the environmental conditions of a site based on all available information. Generally speaking: A SCM is a SAR and as a result this presentation is based on and build around the site SAM Site Assessment Report Checklist which includes the majority of the contents for a SCM.

6 Goals of an SCM Provide a clear understanding of the existing environmental site conditions based on accessible/available information Minimize or eliminate erroneous activities Based on the SCM provide a clear recommendation to move to closure Utilize existing regulatory framework as a guide to closure (MCLs/Low Risk Sites) With the previous definition in mind, what are the goals of a SCM. 1. Utilize previous SCMs to ensure wells are installed appropriately and remediation alternatives are viable. 2. Provide and interpret all applicable data a. Use example of site with multiple wells screened below GW after initial assessment determined DTW. 3. What should be done next to move the case to closure. Remember that DEH is not managing the case, we are participating in a guidance role not a management role. 4. Use regulatory framework to guide the case to closure including MCLs, RWQCB has a document for the management of low risk sites, etc.

7 When is a SCM necessary? Whenever assessment activities are conducted for a site. If site circumstances or conditions have changed or data is outdated As part of a health risk assessment or a receptor pathway evaluation As part of any corrective action plan or closure document. Not groundwater monitoring reports since these activities only provide a very limited amount of data as an update. If a site has been inactive for a number of years or other major site changes (i.e. depth to GW change that is significant). Essentially to better understand the relationship between contaminants and receptors (i.e. benzene plume vs. building location). To understand the relationship between contaminants and the proposed remedial strategy.

8 General SCM Characteristics
Every site will include different information depending on its specific circumstances Contains in depth analysis and successful presentation of data Comprehensive in nature including all historical data and pertinent events Includes a clear objective and direction for the site substantiated by the SCM contents Every site is different Depth to water (or estimate) Extent of known or suspected contamination Nearby land use / characteristics / Receptors Presentation and analysis 1. Legible/useful figures 2. Applicable tables with pertinent information (comprehensive) 3. Rational behind decisions/interpretations Comprehensive Comprehensive tables and figures comprehensive (not just copies of previous consultants work unless you can trust and agree with it and a narrative is included to explain it.) Include previous applicable information like a benzene vapor risk evaluation or excavation Only pertinent information should be included Each subsequent assessment should build on the previous assessment (i.e. data from all past assessments must be included) Clear objective and direction 1. What needs to be done next?? Based on your professional experience and the existing SCM are there data gaps that need to be addressed?

9 SCM Summary General Site Characteristics
History, Business type, Surrounding land use, RPs, Location, Geology, Hydrogeology, Receptors, Contaminant(s) etc. Procedure and Contaminant Information Release description, Sampling information, Soil, vapor and groundwater data interpretation (Figures) Discussion Risk discussion (including receptor pathway evaluation), Substantiate interpretations, provide backup Conclusions and Recommendations Trends, Risk and Delineation conclusions, data gaps, and recommendations on what to do next. Keep in mind that DEH uses a risk based closure scheme pursuant to the Fund Contract. General Site Characteristics 1. Playing Field – There’s a lot of information here!! 2. Goals or objective of assessment Procedure and Contaminant Information Assessment procedures (both general and specific) Contaminant data and interpretations (figures and interpretations) Discussion Has any new risk been identified or can previously identified risk be discounted based on new information Data trends, graphs, etc. Interpretation substantiation and backup for Conclusions and Recommendations Conclusions and Recommendations Trends based on discussion and interpretations Risk – what requires additional evaluation Data Gaps What do we do next

10 SCM Contents Site Identification
a. Site address (street name and number, city, state, zip code) b. Name of business at site c. Assessor's Parcel Number (APN) d. DEH Case Number (e.g., H ) e. Property owner (name and mailing address f. Tank owner (name and mailing address) g. Tank operator (name and mailing address) h. Contact person (name, mailing address and phone number) i. Responsible party (name and mailing address) j. Location maps Why do these things need to be in every report? To ensure that all involved are on the same page. Information can be lost with DEH staff change, RP change, consultant changes etc. DEH must be notified when the property changes hands per regulations.

11 SCM Contents Site History/Development/Usage
a. Historical site use (including potential sources of contamination and dates) b. Current site use (including potential sources of contamination and dates) c. Future site use and development plans (type of use, new construction, below-grade structures, proposed excavation work, elevator shafts, vaults, utility trenches) d. Adjacent site uses (Site Vicinity Map) Do not include a chronology of everything that’s ever happened at the site. Keep it applicable and up to date. Adjacent site uses are changing rapidly in this real-estate market.

12 SCM Contents Description of Release and Site Plot Plan
a. Substance(s) released b. Contaminant characterization c. Quantity of substance(s) released (estimate) d. How and when release occurred e. Location of release on site (can be based on data) f. Drawn to scale (indicate scale used) g. North direction arrow h. Streets, structures, and utilities i. Excavation and stockpile locations j. Tank and piping locations (past, existing, proposed) k. Well, boring, and sample locations l. Legend for symbols and abbreviations This information should always be provided WHEN APPLICABLE. Suspected location of release (can be based on contaminant data)

13 Site Plan Showing Utilities and Depths
Standard site plan information General site layout with surrounding streets and names North arrow Scale Onsite structures and buildings USTs, dispensers, and piping Utilities with depths (if applicable) Other pertinent information including surface contours fences etc.

14 SCM Contents Geology, Hydrology and Hydrogeology
a. Local geology description b. Site geology description (based on borings) c. Topography d. Surface drainage and surface-water bodies in vicinity e. RWQCB basin plan hydrographic unit, subunit identification, and aquifer sensitivity status. f. Groundwater elevation measurements and depth to groundwater g. Groundwater gradient and direction of groundwater flow h. Description of all groundwater aquifers i. Known or probable contaminant migration patterns (consider hydrogeology, groundwater gradient, utility trenches, etc.) j. Source of information a. Differentiate between local geology and site geology (indication of fill vs. native) h. Alluvial or fracture flow

15 SCM Contents Delineation of Contamination (Soil)
a. Summary table(s) of analytical data with sample identification, date, depth, location, analysis method(s), results, etc. b. Map(s) showing horizontal extent of soil contamination, probable contamination sources, contaminant migration pathways, well and boring locations, sample locations, and sample results c. Cross sections showing vertical and horizontal extent of soil contamination, contamination source(s), lithology, water table, sample locations, sample results, and underground structures f. Estimated mass/volume of contaminated soil (when applicable) Make sure you include a narrative in addition to the figures to explain What the figures depict Exceptions, special circumstances, or noteworthy information General discussions or conclusions based on data and figures.

16 Soil Concentration and Contour Map Example
Important items to include on a map view concentration map 1. Concentrations of CoC’s with depths (in this case the samples were differentiated by color for UST removal samples versus borings) 2. Cross section lines 3. Contaminant contour line with explanation.

17 Cross Section Example Figure
Important items to include on a cross section Depth and elevation UST pit Underground Utilities Laboratory analytical data Measured groundwater range Scale Liquid-Phase Hydrocarbons Contoured soil contamination that matches the plan view figure.

18 SCM Contents Delineation of Contamination (Groundwater)
a. Summary table(s) of analytical data with sample identification, depth, location, analysis method(s) and results b. Map(s) showing horizontal extent of groundwater contamination, well locations, sample results, product thickness in wells, groundwater elevation in wells, groundwater elevation contours, and groundwater flow directions c. Environmental parameters or manmade features which may affect the spread of contamination C. Examples of Environmental parameters or manmade features 1. Utilities, footings, or other subsurface structures 2. Lithology (clay layers, competent rock, etc.)

19 Groundwater Contaminant Contour Map Example
Important items to include on groundwater contour maps Wells with identification Well concentration LPH contour CoC contours (usually logarithmically distributed) Contour line labels Date of sampling

20 SCM Contents Exposure Concerns
a. Contaminant migration pathways description and receptor pathway evaluation b. Man-made pathways (conduits, utilities, vaults, piping, storm drains, etc.) c. Natural pathways (air, soil, surface water, bedrock fractures, groundwater, etc.) d. Impact on biological receptors (people, plants, animals) e. Potential nuisance complaints (odors, eyesore) f. Risk assessment concepts and calculations g. Identify all production and potable water supply wells within feet of the site by means of area site visit, California Department of Water Resources (DWR) records, etc. A receptor pathway evaluation must identify Each receptor (what are we protecting) Contaminants of concern (what are we protecting it from) Each pathway (how will the CoC get from point A to point B.) Quantitative analysis of potential risk with all backup and calculations

21 SCM Contents Sampling a. Protocol description b. Methods
c. Preservation and transport d. Analyses performed e. Chain-of-custody forms f. Sample matrix description (clay, sand, water) g. Laboratory analytical reports (on letterhead) h. Quality assurance/quality control data i. Interpretation of analytical results with respect to previous and current understanding of the site a. Sampling protocol ensures that DEH understanding how the sampling was conducted and provides guidance and consistency to field staff.

22 SCM Contents Stockpiled Soil Management and Site Safety a. Volume
b. Location c. Methods used to prevent aeration, run-off and public access d. Disposal methods e. Copies of manifests f. Site safety/security description g. Community health and safety issues addressed h. Monitoring equipment i. Protective equipment j. Public agency notifications k. Utility notifications (Call USA 48 hours before work by law) Only if applicable.

23 SCM Contents Conclusions, Recommendations, Signature
a. Horizontal and vertical extent of soil and groundwater contamination explanation b. Additional assessment or other recommendations c. Alternative mitigation recommendations d. Signature(s) of report preparer(s) e. Signature(s) and registration number(s) of the registered professional(s) who supervised and is responsible for designated portions of the report f. Authorized signature for the company preparing the report (original signatures required--no draft, unsigned, or electronically signed reports)

24 SCM Contents Appendices a. Well/boring logs
b. Hazardous waste manifests and disposal receipts c. Permits (APCD, Fire Department, Wells, etc.) d. Laboratory data sheets e. Chain-of-custody forms f. Backup information including calculations, notes, photographs, etc. as applicable For all wells and borings installed as part of this assessment. Other applicable boring logs may be necessary as well.

25 Anyone still think this a SCM?

26 Closing Comments Most of the information above will not need to be recreated each time a SCM is submitted and therefore shouldn’t require excessive effort to incorporate into future documents. If this information is included in every SCM there’s less chance of information being lost etc. The number one reason DEH receives for an incomplete SCM is that the information is not available (which usually means not easily available) That was a lot of information, however If site conceptual models are complete: Cases will be turned around more quickly Cases will be managed more efficiently Decrease the work load of all involved. Move the case to closure more quickly while protecting public health.

27 Questions?

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